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At least 919 records · Page 51Linked to original sources
PubMed1992

Backscattered electron imaging by scanning electron microscopy of regenerating peripheral nerve axons immunostained with antineurofilament antibody.

To demonstrate three-dimensional architecture of regenerating axons growing through basal lamina tubes in cryoinjured nerve graft, backscattered electron (BSE) imaging in a scanning electron microscope (SEM) was used to visualize immunostained axons. Regenerating axons immunostained with an antibody against the 200 kD neurofilament protein (RT97) were clearly visualized in BSE images as bright components pursuing an irregular, often spiral course within the basal lamina tubes, and commonly branching within the tubes. The morphology of these structures corresponded closely to that of putative regenerating axons in SEM preparations following application of the potassium hydroxide-collagenase digestion method. The present approach, however, is a considerable improvement on the latter, providing three-dimensional information together with the identification of regenerating axons.

Animals↗
PubMedDate not supplied

[Electron-conformational interactions at the active site of reduced bacterial cytochrome P450cam induced by a substrate and analysis of the electron structure of heme].

Magnetic circular dichroism (MCD) spectra in the Soret region (360-480 nm) of camphor-free and camphor-bound reduced bacterial cytochrome P450cam from Pseudomonas putida were recorded and analysed in the temperature range from 2 K to 290 K. The temperature dependences of the MCD intensity are qualitatively changed by binding of substrate to the enzyme. In the absence of camphor the linear increase of the MCD intensity with 1/T at T < 4.2 K gives evidence for degeneracy or near degeneracy of the ground electronic state. In the presence of substrate the degeneracy is removed and temperature profiles show saturation behaviour at T < 4.2 K and wavelength dependence of their high-temperature parts. The temperature profiles for the long-wavelength region of the Soret band have a maximum approximately at 15 K, whereas the MCD intensity increases in a monotonous manner up to saturation in the short-wavelength region. The wavelength dependence of temperature profiles gives evidence for the co-existence of two different forms of substrate-bound reduced P450cam. The following conclusions were obtained from a theoretical analysis of the temperature profiles. In the absence of substrate there are very small if any rhombic distortions at the heme iron, and a parameter D of axial zero-field splitting is negative (D = -8.3 cm-1 and -6.2 cm-1 for P450cam and P450LM2, respectively). In the presence of substrate the two forms of reduced P450cam have positive parameters D but of different values (D1 = 12 cm-1 and D2 = 28 cm-1), and there are large rhombic distortions at the heme iron. More than two-fold difference between the D values made it possible to isolate temperature-dependent contributions of the two enzyme forms from the total MCD spectra and to simulate the alterations of the MCD spectra with temperature for reduced P450cam in the presence of substrate. Taking into account the drastic effect of substrate binding on the ground electronic state of reduced P450cam one can suggest that substrate binding induces the transition of enzyme from an inactive to an active state.

Binding Sites↗
PubMedDate not supplied

Electron beam dosimetry of Total Skin Electron Therapy (TSET).

Total Skin Electron Therapy (TSET) was carried out using an electron beam with a nominal energy of 6 MeV. The beam was adequately filtered and angled in order to create dual fields. The uniformity of the dose distribution to the patient was 10%. The relative dosimetry of the dual beam was performed using a silicon diode and an ionization chamber in a standard water phantom. X-Omat V films were irradiated in a cylindrical PMMA phantom in order to obtain the dose distribution for the six TSET dual fields used in the treatment. Absolute dosimetry was carried out with a calibrated ionization chamber placed in a cylindrical water phantom. The dose contribution per monitor unit of the single dual beams was determined with this method.

Dose Fractionation, Radiation↗
PubMed1991

Sphincters in the rat pulmonary veins. Comparison of scanning electron and transmission electron microscopic studies.

The microvasculature of the rat lung was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of vascular corrosion casts and tissue sections. Particular emphasis was placed on postcapillary venules, pulmonary venules and small pulmonary veins (small interlobular veins). Casts of lung capillaries appeared inconspicuous with smooth surface. On the casts of pulmonary venules and small pulmonary veins, by contrast, series of narrow annular constrictions, present at regular distances of 20-25 microns, were seen. These constrictions may be drastic, narrowing down the caliber of the vessel up to 50%. In the constrictions the marks of circularly running tubular structures were seen and were interpreted as being caused by circular bands of smooth muscle cells. Tissue sections of the corresponding vascular wall showed the presence of single or grouped smooth muscle cells which regularly formed myoendothelial junctions. These smooth muscle cells are interpreted as sphincters, responsible for the constrictions seen on cast preparations. Axon terminals were not found in spatial relationship to these sphincters. It is suggested that the described venous sphincters are governed by blood-borne and/or endothelium-derived substances and may significantly influence the blood flow.

Animals↗
PubMed1991

[Electron microscopic evidence of aluminum in lysosomes of kidney cells by electron energy loss spectroscopy].

Aluminium effects have increasing attention in long term dialysis of kidney patients and in a number of cerebral diseases. At present, however, there are still many open points concerning its localization and actions in the cell. If using electron spectroscopic imaging (ESI), aluminium could be directly demonstrated in the lysosomes of the kidney cells of uraemic rats experimentally loaded with aluminium. These findings were corroborated by means of electron energy loss spectroscopy (EELS).

Aluminum↗
PubMed1991

Application of electron-donor properties of glucose oxidase and xanthine oxidase for reduction of microsomal NAD(P)H-dependent electron-transport chains.

The reduction of cytochromes b5 and P-450 in mammalian hepatic microsomes by glucose oxidase and xanthine oxidase has been investigated. Under anaerobic conditions cytochrome b5 is reduced by glucose oxidase to the "dithionite" level, while cytochrome P-450 remains oxidized. Under the same conditions xanthine oxidase completely reduces both hemoproteins. Besides, neither glucose oxidase nor xanthine oxidase reduces isolated cytochromes. They can be reduced only after addition of microsomes to incubation media. Only in this case are the cytochromes, both isolated and included in microsomal membranes, reduced. The participation of microsomal flavoproteins in the reduction reaction is discussed. The method suggested makes it possible to substantially decrease the rates of reduction of microsomal hemoproteins, thus permitting the investigation of interactions between microsomal NADH- and NADPH-dependent electron-transport chains and electron carriers.

Animals↗
PubMed1990

Ultrastructural investigation of granulation tissues on the osteoarthritic femoral head. A scanning electron microscopic and transmission electron microscopic study.

From the femoral heads of nine cases of advanced osteoarthritis of hip joint, three categories of granulation tissues with different colors (bright red, dark-red and white granulation tissues) and texture were obtained. After processing, the specimens were observed under scanning electron microscope and transmission electron microscope. With transformation of the granulation tissues from bright red to white, the collagen fibers therein contained gradually changed from fine to thick ones. Nevertheless, the cellular components in these three types of granulation tissues always possessed the characteristics of both fibroblasts and chondrocytes, i.e., fibroblastic configuration with pericellular Type I collagen fibrils bearing 64 nm periodicity; and chondrocytic scallop-shaped cytoplasmic membrane with intracytoplasmic fat droplets and glycogen granules and pericellular Type II collagen fibrils. All these indicated that in osteoarthritis of hip joints, the granulation tissues of the femoral heads transformed eventually into fibrocartilage, irrespective of their color and texture.

Femur Head↗
PubMed1985

Identification of a subpopulation of primary granules in human neutrophils based upon maturation and distribution. Study by transmission electron microscopy cytochemistry and high voltage electron microscopy of whole cell preparations.

Two main classes of primary granules have been identified in human neutrophils by peroxidase cytochemistry and electron microscopy, spherical granules and elongated granules, containing crystals with well-defined periodicity. In the present study, we report another subpopulation of primary granules, distinguishable from the other primary granules by their small size, strong peroxidase reactivity under selective incubation conditions with diaminobenzidine, stage of neutrophil maturation at which they appear, and distinctive morphological characteristics. Early promyelocytes, reacted with diaminobenzidine before fixation, demonstrate no reactivity in the large primary granules, but strong peroxidase activity in the endoplasmic reticulum and Golgi apparatus. At the end of the promyelocyte stage of maturation, when the endoplasmic reticulum decreases in peroxidase reactivity, small, round or elongated granules (100 to 200 nm) are observed, reacting strongly for peroxidase. These small granules persist during maturation. The data suggest that these small granules are packaged after the large primary granules and before the secondary granules. All three classes of primary granules exhibit peroxidase activity when fixed prior to incubation in diaminobenzidine at neutral or alkaline pH. Distinctive morphological characteristics of the small primary granules are observed in circulating neutrophils. The small granules are arranged in chains or clusters primarily at the cell margin or uropod in moving cells and are aligned along the axis of cell polarity. This granule association is more evident in adherent neutrophils, particularly after short incubation with phorbol myristate acetate. Chains consisting of as many as 17 small granules are observed. Stereo high voltage electron microscopy of whole-mount preparations of adherent neutrophils reveals chains of small granules apparently interconnected by microtrabeculae. Thus, the small granules observed in thin sections do not represent a transverse section of elongated granules, and the interconnection of granules by microtrabeculae may determine the arrangement of granules. These data support the existence of subpopulations of primary granules which contain distinct forms of myeloperoxidase.

Bone Marrow↗
PubMed1979

Immunologic techniques for the identification of virion and cell surface antigens by correlative fluorescence, transmission electron and scanning electron microscopy.

The present resolution (75-100 A) of the conventional scanning electron microscope (SEM) and its ability to image the surfaces of large numbers of whole cells in situ permits the approach of problems such as viral and cell surface antigen localization by immunological labeling with visual markers. Identification of virus and cell surface antigens in situ has been accomplished in indirect reactions by conjugated and unconjugated markers. Hemocyanin (Hcy) from whelk, Busycon canniculatum, has been developed as an immunospecific marker for virion and cell surface labeling in the electron microscope. Its size (approximately 30 x 50 nm) and distinct cylindrical shape permit easy visualization in the SEM and TEM. The Hcy method involves the preparation of antisera to Hcy in appropriate hosts for use in an unlabeled antibody macromolecular procedure based exclusively on antigen-antibody affinity to couple the macromolecule to the antigen site. Further correlative data from fluorescence microscopy can be obtained from similarly labeled samples by binding fluorescein to the bridging antibodies used in the Hcy technique. The usefulness of the Hcy marker system was demonstrated using antisera to the major envelope and cell surface glycoprotein (gp70) of Rauscher murine leukemia virus (R-MuLV), a type C retrovirus. The antiserum was shown to bind to the virion and cell surfaces of virus-infected cells in the homologous virus-infected cell system. It also demonstrated the expression of R-MuLV gp70-related antigens on a murine cell line Mm5mt/c1 which produces mouse mammary tumor virus (MuMTV), A type B retrovirus. Furthermore, when used in the Hcy marker system this antiserum was able to distinguish type B from type C budding virus on the same cell. Examples of other marker systems (ferritin, peroxidase, colloidal gold, and latex) used to show anti-gp70 serum reactivity will be presented to demonstrate their applicability to cell surface labeling studies. Methods for the preparation of immunoreagents and labeling of cells are discussed.

Animals↗
PubMed1985

[The first linear electron accelerator Therac 15-Saturne in clinical service. 2. Measurement of electron radiation].

Therac 15-Saturne is a linear accelerator for photon and electron radiation with a double scattering screen system. It has proved its worth during more than three years of clinical use. The dosimetric data of both kinds of radiation correspond to the international requirements for modern therapy units. The trimmer system for electron radiation is equipped with a continuous field size adjustment device for the whole range of field sizes. Thus a fast and precise adjustment is possible without any changing of tubes.

Electronics, Medical↗
PubMed1985

Working at higher magnifications in scanning electron microscopy with secondary and backscattered electrons on metal coated biological specimens and imaging macromolecular cell membrane structures.

Membrane structures of macromolecular dimensions were imaged with high resolution secondary electron type I (SE-I) signal contrasts on metal coated biological specimens. The quality of the surface information was strongly dependent on the signal used for microscopy and on the properties of metal films, i.e., thickness, continuity, structure and decoration effects. Films of 10 nm thickness produced so much type II electrons that identical images were obtained with the conventional SE-II and BSE-II signals. In such images, the type I SE signal was so low that only very weak contrasts were recognizable. If the films--continuous or discontinuous--were composed of large metal aggregates (gold and platinum) a strong micro-roughness contrast was produced by the type II signal. At high magnifications (100,000 x) this background signal greatly reduced the S/N ratio of the SE-I signal. A similar effect was previously shown to be produced by the type III background signal. The type II background signal minimized when continuous films of small aggregates (tantalum and chromium) were applied. SE-I contrast dominated in the image if the film thickness was limited to 1 nm. Additionally, it was found that gold and platinum decorated membrane surface structures, less than 20 nm in size, and did not reveal all the topographic information available (size, shape, orientation spacing of small surface features) but merely displayed center-to-center distances. These decoration effects were avoided and extensive topographic information was obtained through surface coating with Ta or Cr.

Animals↗
PubMed1981

Electron paramagnetic and electron nuclear double resonance of the hydrogen peroxide compound of cytochrome c peroxidase.

We have collected electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectra from the hydrogen peroxide compound of yeast cytochrome c peroxidase, termed ES, employing EPR microwave frequencies of 9.6 and 11.6 GHz. We have measured and analyzed the temperature dependence of the spin-lattice relaxation rate (1/T1) of the paramagnetic center of ES over the temperature range 1.9 to 4 K. In addition, an upper bound to exchange coupling between the ferryl heme and EPR-visible centers of ES has been calculated and expressions for the dipolar interaction between a ferryl heme and a free radical have been derived. These results all confirm that the EPR signal of ES is not associated with an aromatic amino acid radical, and in particular not with a tryptophanyl radical. This conclusion has led us to consider an explanation of the EPR signal in terms of a nucleophilically stabilized methionyl radical.

Binding Sites↗
PubMed1983

Cytochemical methods for the backscattered electron imaging mode of scanning electron microscopy: further applications to the study of human leukemic cells.

The Backscattered Electron Imaging (BEI) mode of Scanning Electron Microscopy (SEM) has been applied to the study of cells stained with various heavy metals in cytochemical reactions. Improvements or modifications of some of these methods and their application to the study of normal and leukemic leukocytes have been evaluated in this report. The results obtained after staining peroxidase-positive granules with osmium, copper, cobalt-nickel and gold-cobalt are compared. Granules containing non-specific esterase activity were demonstrated in the BEI mode after incubation of the cells in Hanker medium and staining with osmium. While sites of acid phosphatase activity were easily localized with a conventional lead method, alkaline phosphatase activity was demonstrated only in the phagocytic vacuoles of cells previously incubated with latex particles and subsequently stained with lead. Cell nuclei were identified in the BEI mode after silver methenamine or bismuth staining. Combining their cell surface and cytochemical characteristics a more accurate identification of the different blood cell types with the SEM becomes possible.

Acid Phosphatase↗
PubMed1981

Particulate evaluation of parenteral nutrition solutions by electronic particle counting and scanning electron microscopy.

The particulate matter contamination of four commercial parenteral nutrition solutions that contained high concentrations of amino acids and dextrose was evaluated. Electron particle counting and scanning electron microscopy (SEM) were used to evaluate the amount of particulate matter over a 24-hour-period. The effect of adding 10 meq calcium and 20 meq phosphate electrolytes on the particulate content of these four solutions was determined also. Both counting methods agreed in the rank order comparison of particulate contamination, in that the Abbott and Travenol solutions contained the fewest particles while the Cutter solutions contained the most. The addition of calcium and phosphate resulted in at least a 50% increase in the mean particle count of all solutions. The SEM analysis showed the mean presence of microscopically large, yet subvisible, particles in the solutions containing phosphate and calcium. All of the solutions followed a previously published relationship between particle number and size. Although all of the solutions contained particulate matter, even the solutions with calcium and phosphate contained fewer particles than allowable by the USP-NF standard.

Drug Contamination↗
PubMed1981

Diagnostic electron microscopy. I. Hematology: differential diagnosis of acute lymphoblastic and acute myeloblastic leukemia. Use of ultrastructural peroxidase cytochemistry and routine electron microscopic technology.

We have described in detail a number of ultrastructural methods which we have found to be useful for the evaluation of hematologic cases submitted to our diagnostic electron microscopic unit. The techniques include the preparation of peripheral blood for study as both buffy coat and cell suspension specimens and the preparation of bone marrow spicules. Ultrastructural methods for the demonstration of glycogen and peroxidase are detailed. The study of such material includes light microscopic study of plastic-embedded, alkaline-Giemsa-stained one micron sections as well as ultrastructural studies. All hematological cases submitted for ultrastructural analysis in a two-year period were reviewed and are presented here. The identification of individual mature cells was relatively simple using light microscopy. Populations of blasts could also easily be recognized. Further differentiation of blasts, primarily lymphoblasts or myeloblasts, was done using ultrastructural cytochemistry where needed. These techniques can easily be done in electron microscopy units concerned with diagnostic work. We submit that pathologists and hematologists should have access to the diagnostic tools described here in order to manage patients with acute leukemia.

Cytological Techniques↗
PubMed1994

Biological electron energy loss spectroscopy in the field-emission scanning transmission electron microscope.

The dedicated scanning transmission electron microscope (STEM) combined with parallel electron energy loss spectroscopy (EELS) provides a very sensitive means of detecting specific elements in small structures. EELS is more sensitive than optimized energy-dispersive X-ray spectroscopy by a factor of about three for calcium. Measurement of such low concentrations requires special processing methods such as difference-acquisition techniques and multiple least squares procedures for fitting reference spectra. By analyzing data recorded at each pixel in a spectrum-image it is possible to map quantitatively the elemental distributions in a specimen. It is possible to prepare cryosections that are sufficiently thin to avoid excessive plural inelastic scattering so analysis can be performed at 100 keV beam energy. Under optimal conditions, a resolution of 10 nm and detection limits of a few atoms are achievable for elements such as calcium, phosphorus and iron. In the field emission STEM certain types of chemical information can be extracted from biological specimens. Valence EELS has been exploited to measure water distributions in frozen hydrated cryosections.

Animals↗
PubMed1976

[A simple opto-electronic device for morphometry of electron micrographs (author's transl)].

Morphometric investigations of light or electron microscopic photographs can be both time consuming and tedious when statistical results are to be obtained. Therefore, an opto-electrical morphometer has been developed to facilitate such investigations. The photograph is placed in between a light source and a grid, and the shape of the object in question is outlined with an electronic pencil. The impulses so produced can be converted into counts which may than be fed into a pocket-sized calculator or micro-computer for further analyses.

Cytological Techniques↗